[C320-list] Speed log problems

[Warren Updike]

Graeme, the other, not so cheap solution, is a solid-state transducer.  The
Airmar CS4500-B17-GAR Ultrasonic Speed Sensor goes for nearly $700. If
interested, check with Airmar, to be sure it is compatible with your
instrument.
Warren

-----Original Message-----
From: Graeme Clark [mailto:cg at skyflyer.co.uk] 
Sent: Friday, July 05, 2013 7:51 AM
To: c320-list at lists.catalina320.com
Subject: Re: [C320-list] Speed log problems

Warren

Good question! I guess my main reason is that we have a high tidal range in
Falmouth (up to 15ft or more) and as you might imagine that can generate
some 'interesting' tidal currents. In order to work out the current our
chart plotter needs an accurate speed through the water (although I guess
what it actually woks out is the combined effect of current and leeway?)
However we can look at current predictions from the charts or the plotter,
so that is not essential; although I don't race, on longer passages and
beats upwind, I do end up tweaking  and adjusting this and that trying to
get a better hull speed and SOG isn't quite the same. However I agree it is
not worth spending a lot of money on!

The idea of a quick underwater localised scrub to see if that restores the
reading (i.e. if it is hull fouling) is a great idea -  shame that the water
here is only about 55F, but I'll manage somehow!

Graeme

> 
> 
> Message: 3
> Date: Thu, 4 Jul 2013 14:35:53 -0400
> From: Warren Updike <wupdike at hotmail.com>
> To: <C320-List at Catalina320.com>
> Subject: Re: [C320-list] Speed log problems
> Message-ID: <BAY156-DS20B52AF312143CB47EC6EDBE7C0 at phx.gbl>
> Content-Type: text/plain; charset="us-ascii"
> 
> Graeme, why do you need it?  Racing maybe?  I gave up on mine: a pain 
> to insert and remove, and would readily be clogged with critters.  
> Now, I rely solely on SOG from GPS.  Yes, I don't get true wind; but, 
> then I've never had it (different story.)  If you really want/need 
> true wind, for about $100 you can get a device that will use SOG and 
> output STW on Sea Talk and forget the headache with the transducer.  
> If interested, let me know and I'll dig up the product info.
> 
> Warren & Pattie Updike
> 1994 C320 #62 "Warr De Mar"
> 
> -----Original Message-----
> From: Graeme Clark [mailto:cg at skyflyer.co.uk]
> Sent: Thursday, July 04, 2013 5:37 AM
> To: c320-list at lists.catalina320.com
> Subject: [C320-list] Speed log problems
> 
> Our original fitted instrumentation (#303, 1996) was ray marine ST50+ 
> Tridata and two years ago we fitted a replacement Ray transducer 
> paddlewheel. This is located directly beneath the two smaller drawers 
> in the forepeak cabin, pretty much on the centreline, with the depth 
> transducer next to it.
> 
> I am having a real problem calibrating the instrument. earlier in the 
> year we set a calibration factor of around 0.80 and now it has had to 
> be change to 2.00 to get anywhere near a sensible reading.
> 
> I regularly withdraw the transducer and clean it for any fouling and 
> other marine life and even pushed out the axle pin, to enable a really 
> thorough cleaning and gave everything a squirt of silicone spray 
> lubricant before reassembly, but still the calibration changes
> 
> I can only come up with two theories: (1) the instrument or transducer 
> is faulty or (2) other fouling and marine growth on the hull in front 
> of the transducer is affecting the water flow over the paddle wheel as 
> the season progresses.
> 
> I'd be grateful for any other suggestions and also for an efficient 
> way to trouble shoot without simply replacing every single item piece 
> by piece!  I guess a haul out and scrub would initially show whether 
> the hull fouling was a factor, but (where I am) that is the bets part 
> of $500. A new transducer is about the same and a replacement  
> instrument (ST60+ is nearest available type that is compatible) would 
> be $3-400 I think. If I end up doing all three that is and expensive
trouble shooting exercise!
> 
> Graeme
> (Simia, #303, Falmouth, England)
> 
>